Lukáš Klein (born 22 March 1998) is a Slovak tennis player. Klein has a career-high ATP singles ranking of World No. 136, achieved on 28 November 2022. He also has a career-high doubles ranking of World No. 240, achieved on 5 April 2021. Klein has reached 12 career singles finals, with a record of 8 wins and 4 losses, including 2 ATP Challenger titles and the rest on the ITF Futures Tour. Additionally, he has reached 11 career doubles finals, with a record of 5 wins and 6 losses, including a 1–3 result in ATP Challenger finals.